The following example illustrates how both principles of probability can be comb

Question

The following example illustrates how both principles of probability can be combined to solve problems in genetics. Probability can also be a useful tool in predicting the results of dihybrid and trihybrid matings. For example, in mating AaBb × AaBb, one would expect 1/4 of the progeny to be AA, 2/4 Aa, and 1/4 aa, or 3/4 4- to 1/4 aa. Likewise, 1/4 should be BB, 2/4 Bb, and 1/4 bb, or 3/4 B- to 1/4 bb. Now, if the A(a) and B(b) genes are independently assorting, one would expect 34 × 3/4 = 9/ proach in answering the following series of questions. If AaBb probability that the offspring will have 16 of the progeny to be A-B-,1/4 × 1/4 to be AAbb, and so forth. Use this ap- is mated to AaBb, what is the /y) a. either the phenotype aal-or the genotype aabb Lyyx31.) b, either the genotype aabb or the genotype AaBb? 4-x-y aabb or the genotype Aabbyx -nara) t (½ 2): 5/16 1 Note that the theoretical expectation from the cross Cex cc is a 3:1 ratio. However, when only our progeny are pro- duced, the probability is actually less than one balf (27/64) that the expected 3:1 ratio will be obtained! Thus, geneticists generally favor experimental organisms that produce many progeny so that theoretically expected ratios can be more read ily approximated

Explanation / Answer

Applying the Mendelian Laws of Inheritance (Segregation, Independent Assortment, Dominance):

Genotype = AaBb * AaBb
Gametes = AB, Ab, aB, ab * AB, Ab, aB, ab
Possibility of getting Phenotype aaB- = 1/4 chances of aa * 3/4 chances of BB, Bb, bB = 3/16
Possibility of getting Genotype aabb = 1/4 chances of aa * 1/4 chances of bb = 1/16
Possibility of getting Phenotype aaB- or Genotype aabb = 3/16 + 1/16 = 1/4

Possibility of getting Genotype aabb = 1/4 chances of aa * 1/4 chances of bb = 1/16
Possibility of getting Genotype AaBb = 1/2 chances of aa * 1/2 chances of bb = 1/4 = 4/16
Possibility of getting Genotype aabb or Genotype AaBb = 1/16 + 4/16 = 5/16

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.